As shown in FIG. 7, an inner mirror such as a room mirror, back mirror or the like is installed at the upper position in front of a driver in the inside of an automobile occasionally by using a method whereby a mirror base 41 is installed on the inner side surface 44 of a front wind-shield glass 43 with an adhesive 42 and an inner mirror 45 is attached to the mirror base 41. It is known to use a paste-like silicone rubber adhesive or a polyurethane rubber adhesive having a fluidity and also having excellent heat-resistance, durability and weather-resistance or a thermoplastic polyvinyl butyral film for bonding an inner mirror base of an automobile to the surface of a front wind-shield glass. Particularly, the thermoplastic polyvinyl butyral film is widely used in European and American countries since it can be easily and conveniently bonded simultaneously with the preparation of a bilayer glass.
However, the polyvinyl butyral film has a disadvantage that it has a property of easily absorbing moisture, and its adhesive force lowers substantially upon absorption of moistures, whereby the attached inner mirror is likely to fall off naturally by a shock or the like during driving. For this reason, a dealer must take the trouble to always prepare an adhesive for an accidental falling off. Furthermore, the polyvinyl butyral film has another disadvantage that it becomes too soft to retain its adhesive force because of the thermoplasticity, thereby the inner mirror naturally falling off when the temperature of a wind-shield rises to a temperature from 60.degree. C. to 80.degree. C.
Moreover, the paste-like adhesive such as polyurethane or silicone rubber has an unsatisfactory external appearance, and also has a problem that a bonding operation including a finish work during the bonding step and a finish work after curing the adhesive, is complex since a mirror base is installed on a window-shield by coating the adhesive on a mirror base and then attaching the adhesive-coated mirror base to the window-shield. Particularly, in the case of the polyurethane type adhesive having a poor UV ray-shielding property, a bonding step is more complicated since a mirror base is installed on a glass plate by coating a black type ceramic color frit on the glass plate, baking the coating and then bonding the mirror base to the glass plate through the baked black type ceramic color frit layer interposed therebetween to shield UV ray of the sun's rays. Furthermore, in the case of using the polyurethane adhesive different from the case of using the polyvinyl butyral film, it is impossible to bond the mirror base simultaneously with the preparation of a bilayer glass, and there is a fear that its manufacturing cost is increased since an independent manufacturing step and equipment are required.
An object of this invention is to provide a structure for installing a mirror base on a glass plate and a method of installing the mirror base on the glass plate, which do not have the above-mentioned disadvantages of the prior art.